A sliding-type fastener for an accessory chain, as described in Japanese patent number 3114868, has been proposed which is comprised of a hollow sphere with a donut-like elastic disk fitted in the hollow sphere, where the accessory chain is inserted into a through hole on the elastic disk and into a pair of through holes on the hollow sphere. By having an outer surface of the elastic disk tightly pressed against an inner wall surface of the hollow sphere, the elastic disk is held in place within the hollow sphere by the elasticity.
As mentioned above, since the outer surface of the elastic disk is tightly pressed against the inner wall surface of the hollow sphere, the elastic disk must be made of an elastic material that is relatively hard and semi-flexible instead of a one comprised with high elasticity and high flexibility in order to maintain the pressure force. Further, an outer diameter of the elastic disk must be larger than an inner diameter of the hollow sphere. As a result, the large elastic disk is forcefully pressed through the pair of through holes on the hollow sphere and to the inside of the hollow sphere by using a wire. However, this insertion work is a hard task and may damage the elastic disk during the insertion process.
Further, in order to press-in the relatively hard and semi-flexible elastic disk mentioned above through the pair of through holes on the hollow sphere, the elastic disk must inevitably be made thinner. As a result, the elastic disk may be broken or deteriorated over a long period of time as the accessory chain is repeatedly slid back and forth, thereby shortening its life span and lowering the quality of the product. This is a fatal problem for the accessory chain. Since the accessory chain is inserted through the thin and relatively hard elastic disk and slid back and forth, the smoothness of the sliding motion decreases over time and becomes harder to use.